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1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H
11#define _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H
12
13#include <__algorithm/copy_n.h>
14#include <__assert>
15#include <__charconv/tables.h>
16#include <__config>
17#include <cstdint>
18#include <limits>
19
20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21# pragma GCC system_header
22#endif
23
24_LIBCPP_PUSH_MACROS
25#include <__undef_macros>
26
27_LIBCPP_BEGIN_NAMESPACE_STD
28
29namespace __itoa {
30
31_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append1(char* __first, uint32_t __value) _NOEXCEPT {
32 *__first = '0' + static_cast<char>(__value);
33 return __first + 1;
34}
35
36_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append2(char* __first, uint32_t __value) _NOEXCEPT {
37 return std::copy_n(&__digits_base_10[__value * 2], 2, __first);
38}
39
40_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append3(char* __first, uint32_t __value) _NOEXCEPT {
41 return __itoa::__append2(__itoa::__append1(__first, __value / 100), __value % 100);
42}
43
44_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append4(char* __first, uint32_t __value) _NOEXCEPT {
45 return __itoa::__append2(__itoa::__append2(__first, __value / 100), __value % 100);
46}
47
48_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append5(char* __first, uint32_t __value) _NOEXCEPT {
49 return __itoa::__append4(__itoa::__append1(__first, __value / 10000), __value % 10000);
50}
51
52_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append6(char* __first, uint32_t __value) _NOEXCEPT {
53 return __itoa::__append4(__itoa::__append2(__first, __value / 10000), __value % 10000);
54}
55
56_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append7(char* __first, uint32_t __value) _NOEXCEPT {
57 return __itoa::__append6(__itoa::__append1(__first, __value / 1000000), __value % 1000000);
58}
59
60_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append8(char* __first, uint32_t __value) _NOEXCEPT {
61 return __itoa::__append6(__itoa::__append2(__first, __value / 1000000), __value % 1000000);
62}
63
64_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append9(char* __first, uint32_t __value) _NOEXCEPT {
65 return __itoa::__append8(__itoa::__append1(__first, __value / 100000000), __value % 100000000);
66}
67
68template <class _Tp>
69_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __append10(char* __first, _Tp __value) _NOEXCEPT {
70 return __itoa::__append8(__itoa::__append2(__first, static_cast<uint32_t>(__value / 100000000)),
71 static_cast<uint32_t>(__value % 100000000));
72}
73
74_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*
75__base_10_u32(char* __first, uint32_t __value) _NOEXCEPT {
76 if (__value < 1000000) {
77 if (__value < 10000) {
78 if (__value < 100) {
79 // 0 <= __value < 100
80 if (__value < 10)
81 return __itoa::__append1(__first, __value);
82 return __itoa::__append2(__first, __value);
83 }
84 // 100 <= __value < 10'000
85 if (__value < 1000)
86 return __itoa::__append3(__first, __value);
87 return __itoa::__append4(__first, __value);
88 }
89
90 // 10'000 <= __value < 1'000'000
91 if (__value < 100000)
92 return __itoa::__append5(__first, __value);
93 return __itoa::__append6(__first, __value);
94 }
95
96 // __value => 1'000'000
97 if (__value < 100000000) {
98 // 1'000'000 <= __value < 100'000'000
99 if (__value < 10000000)
100 return __itoa::__append7(__first, __value);
101 return __itoa::__append8(__first, __value);
102 }
103
104 // 100'000'000 <= __value < max
105 if (__value < 1000000000)
106 return __itoa::__append9(__first, __value);
107 return __itoa::__append10(__first, __value);
108}
109
110_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*
111__base_10_u64(char* __buffer, uint64_t __value) _NOEXCEPT {
112 if (__value <= UINT32_MAX)
113 return __itoa::__base_10_u32(__buffer, static_cast<uint32_t>(__value));
114
115 // Numbers in the range UINT32_MAX <= val < 10'000'000'000 always contain 10
116 // digits and are outputted after this if statement.
117 if (__value >= 10000000000) {
118 // This function properly deterimines the first non-zero leading digit.
119 __buffer = __itoa::__base_10_u32(__buffer, static_cast<uint32_t>(__value / 10000000000));
120 __value %= 10000000000;
121 }
122 return __itoa::__append10(__buffer, __value);
123}
124
125# if _LIBCPP_HAS_INT128
126/// \returns 10^\a exp
127///
128/// \pre \a exp [19, 39]
129///
130/// \note The lookup table contains a partial set of exponents limiting the
131/// range that can be used. However the range is sufficient for
132/// \ref __base_10_u128.
133_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline __uint128_t __pow_10(int __exp) _NOEXCEPT {
134 _LIBCPP_ASSERT_INTERNAL(__exp >= __pow10_128_offset, "Index out of bounds");
135 return __pow10_128[__exp - __pow10_128_offset];
136}
137
138_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*
139__base_10_u128(char* __buffer, __uint128_t __value) _NOEXCEPT {
140 _LIBCPP_ASSERT_INTERNAL(
141 __value > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fails when this isn't true.");
142
143 // Unlike the 64 to 32 bit case the 128 bit case the "upper half" can't be
144 // stored in the "lower half". Instead we first need to handle the top most
145 // digits separately.
146 //
147 // Maximum unsigned values
148 // 64 bit 18'446'744'073'709'551'615 (20 digits)
149 // 128 bit 340'282'366'920'938'463'463'374'607'431'768'211'455 (39 digits)
150 // step 1 ^ ([0-1] digits)
151 // step 2 ^^^^^^^^^^^^^^^^^^^^^^^^^ ([0-19] digits)
152 // step 3 ^^^^^^^^^^^^^^^^^^^^^^^^^ (19 digits)
153 if (__value >= __itoa::__pow_10(38)) {
154 // step 1
155 __buffer = __itoa::__append1(__buffer, static_cast<uint32_t>(__value / __itoa::__pow_10(38)));
156 __value %= __itoa::__pow_10(38);
157
158 // step 2 always 19 digits.
159 // They are handled here since leading zeros need to be appended to the buffer,
160 __buffer = __itoa::__append9(__buffer, static_cast<uint32_t>(__value / __itoa::__pow_10(29)));
161 __value %= __itoa::__pow_10(29);
162 __buffer = __itoa::__append10(__buffer, static_cast<uint64_t>(__value / __itoa::__pow_10(19)));
163 __value %= __itoa::__pow_10(19);
164 } else {
165 // step 2
166 // This version needs to determine the position of the leading non-zero digit.
167 __buffer = __base_10_u64(__buffer, static_cast<uint64_t>(__value / __itoa::__pow_10(19)));
168 __value %= __itoa::__pow_10(19);
169 }
170
171 // Step 3
172 __buffer = __itoa::__append9(__buffer, static_cast<uint32_t>(__value / 10000000000));
173 __buffer = __itoa::__append10(__buffer, static_cast<uint64_t>(__value % 10000000000));
174
175 return __buffer;
176}
177# endif
178} // namespace __itoa
179
180_LIBCPP_END_NAMESPACE_STD
181
182_LIBCPP_POP_MACROS
183
184#endif // _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H
185

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source code of libcxx/include/__charconv/to_chars_base_10.h